Internet-based venues such as websites, chat rooms, blogs, and bulletin boards are becoming an increasingly popular means for HIV-positive men who have sex with men (MSM) to meet potential sex partners. The anonymity, quickness, and convenience offered by online venues allows for numerous potential sex partners to be identified and screened with the possibility to meet in person. However, there are potential health hazards associated with meeting sex partners online, including an increased risk of sexually transmitted infections (STIs), and thus there is an urgent need for online behavioral interventions to help reduce STI/HIV risks associated with Internet-initiated sexual liaisons. This research application requests 3 years of support to conduct developmental intervention studies to design and field test an online, theory-based behavioral risk reduction intervention for HIV-positive MSM who use the Internet to meet potential sex partners. Guided by the Information-Motivation-Behavioral Skills (IMB) model of health promoting behaviors we will conduct 3 stages of intervention development research, as follows: (1) perform initial interviews and focus groups with HIV-positive MSM who use the Internet to meet sex partners. Stage 1 will also bring together expert and community consultants to aid in the intervention development. Based on information gained from rapid formative studies, this first stage of research will directly lead to the development a novel online theory-based sexual risk reduction intervention; (2) test the feasibility and acceptability of the newly developed online STI/HIV risk reduction intervention with a sample of HIV-positive MSM who use the Internet to meet sexual partners. Stage 2 will also involve programming an audio-computer assisted interview for data collection; and (3) conduct a randomized field test to determine the potential efficacy of the risk reduction intervention for MSM who use the Internet to potentially meet sex partners. Participants in the field test will be randomly assigned to either receive the newly developed intervention or a time-matched attention comparison condition. Stage 3 will include testing for differences between groups on behavioral risk and Internet use outcomes across a 6-month follow-up period. We will also examine the intervention effects on mediating and moderating constructs of information, motivation, and behavioral skills. The proposed intervention research will therefore develop new STI/HIV prevention strategies delivered exclusively online for use with people living with HIV/AIDS (PLWHA) who use the Internet to meet potential sex partners. The results from this study will provide preliminary data on which to conduct a larger-scale, randomized controlled clinical trial in the future.